I run primarily KDE, mostly stable, with select ~amd64, so I know this might come down to me picking up the pieces, but I'd really like to understand what's going on.
After the latest sync, I've been able to upgrade everything except kdelibs.

The following USE changes are necessary to proceed:
(see "package.use" in the portage(5) man page for more details)
# required by kde-apps/plasma-runtime-16.04.3::gentoo
# required by kde-apps/kqtquickcharts-16.08.3::gentoo
# required by @selected
# required by @world (argument)
>=kde-frameworks/kdelibs-4.14.28 webkit

I have -webkit set in make.conf. The best I can follow is that the kdelibs ebuild sets WEBKIT_REQUIRED="optional" which the kde-base eclass turns into the required USE. I cannot figure out how either plasma-runtime or kqtquickcharts is involved with this use flag, other than being what pulls in kdelibs.

I'm not striclty against setting the use flag for this one package, but I'd really like to understand why it is being required.

Prior to introducing this use flag, kdelibs and any package inheriting kde4-base have always unconditionally pulled in qtwebkit:4. Disabling it both drops the dependency and leads to kdelibs missing kdewebkit. Now, for plasma-runtime:4 I can tell you that it definitely needs that as I made the commit._________________backend.cpp:92:2: warning: #warning TODO - this error message is about as useful as a cooling unit in the arctic

Prior to introducing this use flag, kdelibs and any package inheriting kde4-base have always unconditionally pulled in qtwebkit:4. Disabling it both drops the dependency and leads to kdelibs missing kdewebkit. Now, for plasma-runtime:4 I can tell you that it definitely needs that as I made the commit.

Please ask that equery. As far as I can tell, it is an integral runtime part for Plasma-4 plasmoids._________________backend.cpp:92:2: warning: #warning TODO - this error message is about as useful as a cooling unit in the arctic

@eccerr0r: I have no idea how I missed that plasma-runtime set WEBKIT_REQUIRED="always". Thanks for pointing it out.

@asturm: I've got webkit-gtk on my mind from a completely separate issue. I've got much less concern with qtwebkit. What I can't figure out is why it's requiring me to explicitly set webkit now, when the currently installed version seems to have just assumed it. However - no point in trying to track that down, since I've altered my use flags too much lately. Time to really try to clean them up.

I also have to figure out whether I really need kqtquickcharts or not. Nothing if formally depending on it, but I do have a few manually installed programs, one of which might need it, but tracking that down is not high on my current todo list.

What I can't figure out is why it's requiring me to explicitly set webkit now, when the currently installed version seems to have just assumed it.

Because previously it was not optional on kdelibs. So now that it is optional, plasma-runtime which needs it must make sure that it is set. Every time you create options for packages it makes things a little more complicated on dependencies._________________backend.cpp:92:2: warning: #warning TODO - this error message is about as useful as a cooling unit in the arctic